a muscle fibre twitch is abrupt or all or none. a muscle contraction is smooth and...

a muscle fibre twitch is abrupt or all or none. a muscle contraction is smooth and graded. explain why

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Expert Solution

Twitch

A muscle twitch is a contraction of muscel in respone to stimulus.
This is an isolated contraction that can last for few milliseconds.
The contraction occurs when the stimulus crosses the threshold.
Hence it is called all- or none phenomenon. If stimulus is stronge enough to cross threshold there is action potential otherwise, no.
But this single twitch does not produce significant muscle activity.

Muslce contraction

A muscle contraction is smooth and graded.
Here, a series of action potential to fibre is necessary to produce sustained muscle contraction.
Once action potential is produced, it sustains over a longer period and travels larger distances.
The contraction can be modified by input from nervous stem to prpduce varying amount of force - this is called graded muscle response.
Smooth response is achived by summation of responses to successive stimuli and recruitment of motor units.

Sydney Mullin answered 1 year ago

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